[Fluffy]

Antrax, on 2012-January-24, 01:22, said:

3♣ Does promise extras, the problem is we hadn't discussed in depth what "extras" really means, in this context. It's 15+ HCP, but that's pretty much all we defined. I deliberated between 3N and 4N, but eventually decided to devalue my hand since partner must be imbalanced (5-4-3-1 or more) and if he had three diamonds, 3♦ would also show extras here. So, partner has at most one diamond, thus I devalued my diamond holding and decided I'll try for most overtricks in 3NT and forget about 6.

You can play whatever style you want, and you won´t be alone, but I like 3♦ direct raise to show 4 cards and I think most people do the same. It doesn´t show extras BTW, it is forcing but not neccesarilly with extras.

I bid 1♠-2♦ with 4 cards often (2443 shape for example, and some hands with 3 spades as well), althou this is not mainstream nowdays and many people do promise 5 diamonds.

[Antrax]

"Our" style is lifted directly from Mike Lawrence's CD. I'm pretty sure he advocates supporting with three cards + extras.